Notebook[List[Cell[BoxData[List[FormBox[RowBox[List[RowBox[List[RowBox[List["\[LeftBracketingBar]", FractionBox[RowBox[List[SuperscriptBox["\[Delta]", "2"], "\[Psi]"]], RowBox[List["\[Delta]", " ", SuperscriptBox["z", "2"]]]], "\[RightBracketingBar]"]], RowBox[List["<<", RowBox[List["\[LeftBracketingBar]", FractionBox[RowBox[List[SuperscriptBox["\[Delta]", "2"], "\[Psi]"]], RowBox[List["\[Delta]", " ", SuperscriptBox["x", "2"]]]], "\[RightBracketingBar]"]]]]]], ",", RowBox[List["\[LeftBracketingBar]", FractionBox[RowBox[List[SuperscriptBox["\[Delta]", "2"], "\[Psi]"]], RowBox[List["\[Delta]", " ", SuperscriptBox["y", "2"]]]], "\[RightBracketingBar]"]], ",", RowBox[List["2", "k", RowBox[List["\[LeftBracketingBar]", FractionBox["\[Delta]\[Psi]", RowBox[List["\[Delta]", " ", "z"]]], "\[RightBracketingBar]"]]]]]], TraditionalForm], FormBox[RowBox[List[RowBox[List[RowBox[List[SubsuperscriptBox["\[Del]", "t", "2"], "\[Psi]"]], "+", RowBox[List["j", " ", "2", "k", FractionBox["\[Delta]\[Psi]", RowBox[List["\[Delta]", " ", "z"]]]]]]], "=", "0"]], TraditionalForm]]], "Input"]]]